1. Field of the Invention
The invention relates generally to rotor bearings, and more particularly to rotor bearings that employ an axial groove at the outer periphery thereof to facilitate axial fluid flow through the bearing.
2. Related Art
Oil and natural gas are often produced by drilling wells into oil reservoirs and then pumping the oil and gas out of the reservoirs through the wells. If there is insufficient pressure in the well to force these fluids out of the well, it may be necessary to use an artificial lift system in order to extract the fluids from the reservoirs. A typical artificial lift system employs an electric submersible pump which is positioned in a producing zone of the well to pump the fluids out of the well.
An electric submersible pump system includes a pump and a motor which is coupled to the pump and drives the pump. The electric submersible pump system may also include seals, gauge packages and other components. Because they are designed to fit within the borehole of a well, electric submersible pump systems are typically less than ten inches wide, but may be tens of meters long. The motor of an electric submersible pump system may produce hundreds of horsepower.
The motor of the electric submersible pump system is typically an AC induction motor. The motor has a stator that is cylindrical with a coaxial bore. A rotor is coaxially positioned within the bore of the stator. The rotor is coupled to a shaft so that rotation of the rotor turns the shaft. Bearings hold the rotor in position within the bore of the stator and allow the rotor to rotate within the bore.
It is important to the longevity of the motor that the bearings not be permitted to rotate against the stator. If the bearings are allowed to rotate against the stator, the stator may experience unnecessary wear and eventual damage to the electrical wires contained within the stator. This may result in the failure of the motor. Despite the need to prevent the bearings from rotating against the stator, it is also important that the bearings must be able to move axially within the stator. Allowing this axial movement facilitates assembly of the motor and also allows the bearings and rotors to move within the stator in response to thermal expansion of the motor components.
These requirements may be met by providing a ring around the periphery of each bearing that impedes the rotation of the bearing against the stator, but allows axial movement of the bearing with respect to the stator. Because the ring provides an interference fit between the bearing and the stator, it will be referred to herein as an interference ring. The interference ring may be, for example, an elastomeric T-ring, or a coil spring which fits within a circumferential groove or channel or the periphery of the bearing and extends outward from the groove to a greater diameter than the outer diameter of the bearing.